The present application relates to a display that employs organic light-emitting elements having a transferred light-emitting layer obtained by a thermal transfer method.
As one of manufacturing methods for an organic light-emitting element, a pattern fabrication method employing thermal transfer has been disclosed. In the thermal transfer method, a donor component arising from formation of a transfer layer containing a light-emitting material over a support is formed. Subsequently, this donor component is disposed to face an acceptor substrate for forming an organic light-emitting element, and the transfer layer is transferred to the acceptor substrate by irradiation with a radiant ray under a low-pressure environment. As the support, a rigid material such as glass is used in some cases (refer to e.g. Japanese Patent Laid-Open No. 2006-309994 (Patent document 1)), and a flexible film is used in other cases (refer to e.g. Japanese Patent Laid-Open No. 2003-168569 (Patent document 2)). In the latter cases, the transfer is carried out in such a was that the donor component is brought into complete contact with an electrode over the acceptor substrate. In the former cases, an insulating layer for defining a light-emmission area is provided over the acceptor substrate. Subsequently, the irradiation with a radiant ray is performed in the state in which the donor substrate is separated from the acceptor substrate by the distance equivalent to the height of this insulating layer, to thereby sublime or evaporate the transfer layer, so that the transfer layer is transferred to the acceptor substrate.
However, as described in Patent document 1, if a rigid material such as glass is used as the support or the donor component, there is room for improvement in the size and shape of the insulating layer for defining the light-emission area and the width and position of the transfer pattern, for suppression of the distribution of the film thickness of the transferred light-emitting layer in the light-emission area and color mixing into an adjacent light-emission area.
In Japanese Patent Laid-Open No. 2003-168569, countermeasures against a fringe pattern in a transfer method of subliming or evaporating a transfer layer are disclosed. However, fundamental measures to suppress the distribution of the film thickness of the transferred light-emitting layer in the light-emission area and to prevent color mixing are not described in this document.
Furthermore, there is a fear that so-called reverse transfer occurs in the transfer step as shown in FIG. 30A. Specifically, in the transfer step, a donor substrate 840 on which a transfer layer 850 is formed is brought into tight contact with, by using pressure difference from the atmospheric pressure, an acceptor substrate 811 over which a first electrode 813, an insulating layer 814, and a hole injection layer and hole transport latter 815AB are formed. Therefore, the tight-contact pressure by the donor substrate 840 possibly causes pressure-transfer of the already-deposited hole injection layer and hole transport layer 815AB. Such a reverse transfer phenomenon readily occurs when heating by laser light at the time of the transfer is added to the pressuring by the donor substrate 840. If the reverse transfer occurs, the deposited surface of the hole injection layer and hole transport layer 815AB over the acceptor substrate 811 is disturbed, and thus current leakage CL through the defect resulting from the reverse transfer will occur as shown in FIG. 30B. This current leakage CL problematically causes streak unevenness and mottled unevenness at the time of the lighting of the display. For this reason, assured suppression of the reverse transfer is desired.